VENICE, La. — Coast Guard officials said an oil rig exploded off the coast of Louisiana, sending four people to hospitals today while two others were believed to be missing. Petty Officer 3rd Class Jonathan Lally, a spokesman for the Coast Guard, did not immediately have information on the conditions of those taken to hospitals. The rig, a production platform owned by Black Elk Energy, is about 25 miles southeast of Grand Isle, La. There was no immediate word if any oil had spilled from the platform. Coast Guard Capt. Peter Gautier said that 28 people were believed to be aboard the rig. Gautier said the platform was not actively producing oil and it is not believed there is any chance for a major environmental disaster. He said initial reports were that maintenance workers were cutting into a pipe and that oil may have escaped, causing the explosion. Lally says two helicopters, an airplane and small boats were sent to the area. He did not know if the fire caused by the explosion had been put out yet. The platform is a production platform, unlike the Deepwater Horizon rig, which was drilling an exploratory well for oil giant BP in mile-deep water well to the east of Friday's reported explosion.